Paper substrate having enhanced print density

ABSTRACT

The present invention relates to a sizing composition that, when applied to paper substrate, creates a substrate, preferably suitable for inkjet printing, having increased print density, print sharpness, low HST, and/or image dry time, the substrate preferably having high brightness and reduced color-to-color bleed as well. In addition, the present invention relates to a method of reducing the HST of a paper substrate by applying the sizing composition to at least one surface thereof. Further, the application relates to methods of making and using the sizing composition, as well as methods of making and using the paper containing the sizing composition.

The present application claims the benefit of priority under 35 USC§119(e) to U.S. Provisional Patent Application 60/732,828, filed Nov. 1,2005, which is hereby incorporated, in its entirety, herein byreference.

FIELD OF THE INVENTION

The present invention relates to a sizing composition that, when appliedto paper substrate, creates a substrate, preferably suitable for inkjetprinting, having increased print density, print sharpness, low HST,and/or image dry time, the substrate preferably having high brightnessand reduced color-to-color bleed as well, in addition, the presentinvention relates to a method of reducing the HST of a paper sub stateby applying the sizing composition to at least one surface thereof.Further, the application relates to methods of making and using thesizing composition, as well as methods of making and using the papercontaining the sizing composition.

BACKGROUND OF THE INVENTION

Ink jet recording systems using aqueous inks are now well known. Thesesystems usually generate almost no noise and can easily performmulticolor recordings for business, home and commercial printingapplications. Recording sheets for ink jet recordings are known. See forexample U.S. Pat. Nos. 5,270,103; 5,657,064; 5,760,809; 5,729,266;4,792,487; 5,405,678; 4,636,409; 4,481,244; 4,496,629; 4,517,244;5,190,805; 5,320,902; 4,425,405; 4,503,118; 5,163,973; 4,425,405;5,013,603; 5,397,619; 4,478,910; 5,429,860; 5,457,486; 5,537,137;5,314,747; 5,474,843; 4,908,240; 5,320,902; 4,740,420; 4,576,867;4,446,174; 4,830,911; 4,554,181; 6,764,726 and 4,877,680, which arehereby incorporated, in their entirety, herein by reference.

However, conventional paper substrates, such as those above remain poorin balancing good print density, HST, color-to-color bleed, printsharpness, and/or image dry time. Accordingly, there is a need toprovide such high-performance functionality to paper substrates usefulin inkjet printing, especially those substrates preferably having highbrightness.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: A first schematic cross section of just one exemplifiedembodiment of the paper substrate that is included in the papersubstrate of the present invention.

FIG. 2: A second schematic cross section of just one exemplifiedembodiment of the paper substrate that is included in the papersubstrate of the present invention.

FIG. 3: A third schematic cross section of just one exemplifiedembodiment of the paper substrate that is included in the papersubstrate of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have discovered a sizing composition that, whenapplied to paper or paperboard substrates, improves the substrate'sprint density, color-to-color bleed, print sharpness, and/or image drytime. Further, the paper substrate preferably has a high brightness.

The sizing composition may contain a pigment. Examples of pigments areclay, calcium carbonate, calcium sulfate hemihydrate, and calciumsulfate dehydrate, calcium carbonate, preferably precipitated calciumcarbonate, in any form including ground calcium carbonate andsilica-treated calcium carbonate. When the pigment is a calciumcarbonate, it may be in any form. Examples include ground calciumcarbonate and/or precipitated calcium carbonate. Commercially availableproducts that are preferred are those offered as Jetcoat 30 fromSpecialty Minerals Inc., Jetcoat MD1093 from Specialty Minerals Inc.,XC3310-1 from Omya Inc, and OmyaJet B5260, C4440 and 6606 from Omya Inc.

The pigment may have any surface area. Those pigments having a highsurface area are included, including those having a surface area ofgreater than 20 square meters/gram, preferably greater than 30 squaremeters/gram, more preferably greater than 50 square meters/gram, mostpreferably greater than 100 square meters/gram. This range includesgreater than or equal to 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55,60, 65, 70, 75, 80, 85, 90, 100 square meters/gram, including any andall ranges and subranges contained therein.

The sizing composition may contain a pigment at any amount. Thecomposition may include from 0 to 99 wt % based upon the total weight ofthe solids in the composition, preferably at least 15 wt %, morepreferably at least 30 wt %, most preferably at least 45 wt % pigmentbased upon the total weight of the solids in the composition. This rangemay include 0, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,75, 80, 85, 90, 100 wt % of pigment based upon the total weight of thesolids in the composition, including any and all ranges and subrangescontained therein. The most preferred amount being about 52 wt % pigmentbased upon the total weight of the solids in the composition.

The sizing composition may contain a binder. Examples of bindersinclude, but are not limited to, polyvinyl alcohol, Amres (a Kymenetype), Bayer Parez, polychloride emulsion, modified starch such ashydroxyethyl starch, starch or derivatives thereof including cationicand oxidized forms and from corn and/or potato for example,polyacrylamide, modified polyacrylamide, polyol, polyol carbonyl adduct,ethanedial/polyol condensate, polyamide, epichlorohydrin, glyoxal,glyoxal urea, ethanedial, aliphatic polyisocyanate, isocyanate, 1,6hexamethylene diisocyanate, diisocyanate, polyisocyanate, polyester,polyester resin, polyacrylate, polyacrylate resin, acrylate, andmethacrylate. While any combination of binders may be used, oneembodiment includes a sizing composition containing starch ormodifications thereof combined with polyvinyl alcohol as multi-componentbinder.

When there is a multicomponent binder system, one embodiment relates toa system including at least starch and deriviates thereof with polyvinylalcohol. In this embodiment, the ratio of starch/PVOH solids based onthe total weight of the solids in the sizing composition may be anyratio so long as both are present in the composition. The sizingcomposition may contain a ratio of starch/PVOH wt % solids based on thetotal weight of the solids in the composition of from 99/1 to 1/99,preferably from 50/1 to 1/5, more preferably at most 10/1 to 1:2, mostpreferably at most 8/1 to 1/1. This range includes 99/1, 50/1, 25/1,15/1, 10/1, 9/1, 8/1, 7/1, 6/1, 5/1, 4/1, 3/1, 2/1, 1/1, 2/3, 1/2, 1/10,1/25, 1/50, 1/99, including any and all ranges and subranges therein.The most preferred starch/PVOH ratio being 6/1.

When polyvinyl alcohol is utilized in the sizing solution and/or in thepaper, polyvinyl alcohol (PVOH) is produced by hydrolyzing polyvinylacetate (PVA). The acetate groups are replaced with alcohol groups andthe higher the hydrolysis indicates that more acetate groups have beenreplaced. Lower hydrolysis/molecular weight PVOH are less viscous andmore water soluble. The PVOH may have a % hydrolysis ranging from 100%to 75%. The % hydrolysis may be 75, 76, 78, 80, 82, 84, 85, 86, 88, 90,92, 94, 95, 96, 98, and 100% hydrolysis, %, including any and all rangesand subranges therein. Preferably, the % hydrolysis of the PVOH isgreater than 90%.

The sizing composition may contain a binder at any amount. The sizingcomposition may contain at least one binder from 0 to 99 wt %,preferably at least 10 wt %, more preferably at least 20 wt %, mostpreferably at least 30 wt % based on the total weight of the solids inthe composition. This range may include 0, 1, 5, 10, 15, 20, 25, 30, 35,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 100 wt % based on the totalweight of the solids in the composition, including any and all rangesand subranges contained therein. The most preferred being about 37 wt %binder based on the total weight of the solids in the composition.

In one embodiment, when the sizing composition contains a binder and apigment, the weight ratio of the binder/pigment may be any ratio. Thebinder pigment weight ratio may be from 99/1 to 1/99, preferably from50/1 to 1/10, more preferably from 25/1 to 1/5, most preferably from10/1 to 1/3. This range includes 99/1, 50/1, 25/1, 10/1, 5/1, 2/1, 1/1,1/2, 2/3, 1/3, 1/4, 1/5, 10/1, 25/1, 50/1, and 99/1, including any andall ranges and subranges therein. The most preferred binder/pigmentweight ratio is 7/10.

The sizing composition may contain at least one nitrogen containingorganic species. Exemplified nitrogen containing organic species arecompounds, oligomers and polymers are those containing one or morequaternary ammonium functional groups. Such functional groups may varywidely and include substituted and unsubstituted amines, imines, amides,urethanes, quaternary ammonium groups, dicyandiamides and the like.Illustrative of such materials are polyamines, polyethyleneimines,polymers and copolymers of diallyldimethyl ammonium chloride (DADMAC),copolymers of vinyl pyrrolidone (VP) with quaternizeddiethylaminoethylmethacrylate (DEAMEMA), polyamides, cationicpolyurethane latex, cationic polyvinyl alcohol, polyalkylaminesdicyandiamid copolymers, amine glycigyl addition polymers,poly[oxyethylene (dimethyliminio) ethylene (dimethyliminio)ethylene]dichlorides. Examples of nitrogen containing species includethose mentioned in U.S. Pat. No. 6,764,726, which is herebyincorporated, in its entirety, herein by reference. The most preferrednitrogen containing species are polymers and copolymers ofdiallyldimethyl ammonium chloride (DADMAC).

The sizing composition may contain at least one nitrogen containingorganic species at any amount. The sizing composition may contain thenitrogen containing species at an amount ranging from 0 to 99 wt %,preferably from 0.5 to 50 wt %, more preferably from 1 to 20 wt %, mostpreferably from 2 to 10 wt % based on the total weight of the solids inthe composition. This range may include 0, 0.5, 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90,100 wt % based on the total weight of the solids in the composition,including any and all ranges and subranges contained therein. In apreferred embodiment, the composition contains about 8 wt % of thenitrogen containing species based on the total weight of the solids inthe composition.

The sizing composition may contain at least one inorganic salt. Suitableinorganic salts may be monovalent and/or divalent and/or trivalent andmay contain any level of hydration complexes thereof. Exemplifiedinorganic salts are those from Groups 1, 2 and 13 from the PeriodicTable of Elements and hydrated complexes thereof, includingmonohydrates, dihydrates, trihydrates, tetrahydrates, etc. The cationicmetal may be sodium, calcium, magnesium, and aluminum preferably. Theanionic counterion to the cationic metal of the inorganic salt may beany halogen such as chloride, boride, fluoride, etc and/or hydroxylgroup(s). The most preferred inorganic salt being sodium chloride.

The sizing composition may contain at least one inorganic salt at anyamount. The sizing composition may contain from 0 to 99 wt %, preferablyfrom 0.25 to 25 wt %, more preferably from 0.5 to 5, most preferablyfrom 1 to 3 wt % of the inorganic salt based on the total weight of thesolids in the composition. This range may include 0, 0.25, 0.5, 1, 2, 3,4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85,90, 100 wt % based on the total weight of the solids in the composition,including any and all ranges and subranges contained therein. In apreferred embodiment, the sizing composition contains about 2.5 wt % ofthe inorganic salt based on the total weight of the solids in thecomposition.

The sizing composition may contain at least one optical brighteningagent (OBA). Suitable OBAs may be those mentioned in U.S. Ser. No.60/654,712 filed Feb. 19, 2005, and U.S. Pat. No. 6,890,454, which arehereby incorporated, in their entirety, herein by reference. The OBAsmay be commercially available from Clariant. Further, the OBA may beeither cationic and/or anionic. Example OBA is that commerciallyavailable Leucophore BCW and Leucophore FTS from Clariant. In oneembodiment, the OBA contained in the sizing composition is cationic.

The sizing composition may contain any amount of at least one anionicOBA. The sizing composition may contain anionic OBA at an amount from 0to 99 wt %, preferably from 5 to 75 wt %, more preferably from 10 to 50wt %, most preferably from 20 to 40 wt % based on the total weight ofthe solids in the composition. This range may include 0, 1, 5, 10, 15,20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 99 wt %anionic OBA based on the total weight of the solids in the composition,including any and all ranges and subranges contained therein. In apreferred embodiment, the sizing composition contains about 35 wt % ofanionic OBA based on the total weight of the solids in the composition.

The sizing composition may contain any amount of at least one cationicOBA. The sizing composition may contain cationic OBA at an amount from 0to 99 wt %, preferably from 0.5 to 25 wt %, more preferably from 1 to 20wt %, most preferably from 5 to 15 wt % based on the total weight of thesolids in the composition. This range may include 0, 1, 5, 10, 15, 20,25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 99 wt % anionicOBA based on the total weight of the solids in the composition,including any and all ranges and subranges contained therein. In apreferred embodiment, the sizing composition contains about 8 wt % ofcationic OBA based on the total weight of the solids in the composition.

The present invention also relates to a paper substrate containing anyof the sizing compositions described above.

The paper substrate contains a web of cellulose fibers. The source ofthe fibers may be from any fibrous plant. The paper substrate of thepresent invention may contain recycled fibers and/or virgin fibers.Recycled fibers differ from virgin fibers in that the fibers have gonethrough the drying process at least once.

The paper substrate of the present invention may contain from 1 to 99 wt%, preferably from 5 to 95 wt %, most preferably from 60 to 80 wt % ofcellulose fibers based upon the total weight of the substrate, including1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85,90, 95 and 99 wt %, and including any and all ranges and subrangestherein.

While the fiber source may be any, the preferable sources of thecellulose fibers are from softwood and/or hardwood. The paper substrateof the present invention may contain from 1 to 100 wt %, preferably from5 to 95 wt %, cellulose fibers originating from softwood species basedupon the total amount of cellulose fibers in the paper substrate. Thisrange includes 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,70, 75, 80, 85, 90, 95, and 100 wt %, including any and all ranges andsubranges therein, based upon the total amount of cellulose fibers inthe paper substrate.

The paper substrate of the present invention may contain from 1 to 100wt %, preferably from 5 to 95 wt %, cellulose fibers originating fromhardwood species based upon the total amount of cellulose fibers in thepaper substrate. This range includes 1, 2, 5, 10, 15, 20, 25, 30, 35,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 100 wt %, includingany and all ranges and subranges therein, based upon the total amount ofcellulose fibers in the paper substrate.

When the paper substrate contains both hardwood and softwood fibers, itis preferable that the hardwood/softwood ratio be from 0.001 to 1000.This range may include 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2,0.5, 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75,80, 85, 90, 95, 100, 200, 300, 400, 500, 600, 700, 800, 900, and 1000including any and all ranges and subranges therein and well as anyranges and subranges therein the inverse of such ratios.

Further, the softwood and/or hardwood fibers contained by the papersubstrate of the present invention may be modified by physical and/orchemical means. Examples of physical means include, but is not limitedto, electromagnetic and mechanical means. Means for electricalmodification include, but are not limited to, means involving contactingthe fibers with an electromagnetic energy source such as light and/orelectrical current. Means for mechanical modification include, but arenot limited to, means involving contacting an inanimate object with thefibers. Examples of such inanimate objects include those with sharpand/or dull edges. Such means also involve, for example, cutting,kneading, pounding, impaling, etc means.

Examples of chemical means include, but is not limited to, conventionalchemical fiber modification means including crosslinking andprecipitation of complexes thereon. Examples of such modification offibers may be, but is not limited to, those found in the following U.S.Pat. Nos. 6,592,717, 6,592,712, 6,582,557, 6,579,415, 6,579,414,6,506,282, 6,471,824, 6,361,651, 6,146,494, H1,704, 5,731,080,5,698,688, 5,698,074, 5,667,637, 5,662,773, 5,531,728, 5,443,899,5,360,420, 5,266,250, 5,209,953, 5,160,789, 5,049,235, 4,986,882,4,496,427, 4,431,481, 4,174,417, 4,166,894, 4,075,136, and 4,022,965,which are hereby incorporated, in their entirety, herein by reference.Further modification of fibers is found in United States patentapplications having Application No. 60/654,712 filed Feb. 19, 2005;11/358,543 filed Feb. 21, 2006; 11/445,809 filed Jun. 2, 2006; and11/446,421 filed Jun. 2, 2006, which may include the addition of opticalbrighteners (i.e. OBAs) as discussed therein, which are herebyincorporated, in their entirety, herein by reference.

One example of a recycled fiber is a “fine”. Sources of “fines” may befound in SaveAll fibers, recirculated streams, reject streams, wastefiber streams. The amount of “fines” present in the paper substrate canbe modified by tailoring the rate at which such streams are added to thepaper making process.

The paper substrate preferably contains a combination of hardwoodfibers, softwood fibers and “fines” fibers. “Fines” fibers are, asdiscussed above, recirculated and are any length. Fines may typically benot more that 100 μm in length on average, preferably not more than 90μm, more preferably not more than 80 μm in length, and most preferablynot more than 75 μm in length. The length of the fines are preferablynot more than 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75,80, 85, 90, 95, and 100 μm in length, including any and all ranges andsubranges therein.

The paper substrate may contain fines at any amount. The paper substratemay contain from 0.01 to 100 wt % fines, preferably from 0.01 to 50 wt%, most preferably from 0.01 to 15 wt % based upon the total weight ofthe fibers contained by the paper substrate. The paper substratecontains not more than 0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80,85, 90, 95 and 100 wt % fines based upon the total weight of the fiberscontained by the paper substrate, including any and all ranges andsubranges therein.

The paper substrate may also contain an internal sizing and/or externalsizing composition. The internal sizing composition may be applied tothe fibers during papermaking at the wet end, while the external sizingcomposition may be applied to the fibers via a size press and/or coater.The above mentioned sizing compositions of the present invention may bethe internal and/or external sizing composition contained by the papersubstrate of the present invention.

FIGS. 1-3 demonstrate different embodiments of the paper substrate 1 inthe paper substrate of the present invention. FIG. 1 demonstrates apaper substrate 1 that has a web of cellulose fibers 3 and a sizingcomposition 2 where the sizing composition 2 has minimalinterpenetration of the web of cellulose fibers 3. Such an embodimentmay be made, for example, when a sizing composition is coated onto a webof cellulose fibers.

FIG. 2 demonstrates a paper substrate 1 that has a web of cellulosefibers 3 and a sizing composition 2 where the sizing composition 2interpenetrates the web of cellulose fibers 3. The interpenetrationlayer 4 of the paper substrate 1 defines a region in which at least thesizing solution penetrates into and is among the cellulose fibers. Theinterpenetration layer may be from 1 to 99% of the entire cross sectionof at least a portion of the paper substrate, including 1, 2, 5, 10, 15,20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 99%of the paper substrate, including any and all ranges and subrangestherein. Such an embodiment may be made, for example, when a sizingcomposition is added to the cellulose fibers prior to a coating methodand may be combined with a subsequent coating method if required.Addition points may be at the size press, for example.

FIG. 3 demonstrates a paper substrate 1 that has a web of cellulosefibers 3 and a sizing solution 2 where the sizing composition 2 isapproximately evenly distributed throughout the web of cellulose fibers3. Such an embodiment may be made, for example, when a sizingcomposition is added to the cellulose fibers prior to a coating methodand may be combined with a subsequent coating method if required.Exemplified addition points may be at the wet end of the paper makingprocess, the thin stock, and the thick stock.

The paper substrate may be made by contacting any component of thesizing solution with the cellulose fibers consecutively and/orsimultaneously. Still further, the contacting may occur at acceptableconcentration levels that provide the paper substrate of the presentinvention to contain any of the above-mentioned amounts of cellulose andcomponents of the sizing solution. The contacting may occur anytime inthe papermaking process including, but not limited to the thick stock,thin stock, head box, and coater with the preferred addition point beingat the thin stock. Further addition points include machine chest, stuffbox, and suction of the fan pump. Preferably, the components of thesizing solution are preformulated either together and/or in combinationwithin a single and/or separate coating layer(s) and coated onto thefibrous web via a size press and/or coater.

The paper or paperboard of this invention can be prepared using knownconventional techniques. Methods and apparatuses for forming and makingand applying a coating formulation to a paper substrate are well knownin the paper and paperboard art. See for example, G. A. Smook referencedabove and references cited therein all of which is hereby incorporatedby reference. All such known methods can be used in the practice of thisinvention and will not be described in detail.

The paper substrate may contain the sizing composition at any amount.The paper substrate may contain the sizing composition at an amountranging from 70 to 300 lbs/ton of paper, preferably from 80 to 250lbs/ton of paper, more preferably from 100 to 200 lbs/ton of paper, mostpreferably from 125 to 175 lbs/ton of paper. This range includes, 70,80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220,230, 240, 250, 260, 270 280, 290, and 300 lbs/ton of paper, includingany and all ranges and subranges therein. In a preferred embodiment thepaper substrate contains a size press applied sizing composition at anamount of 150 lbs/ton of paper substrate.

Given the above mentioned preferred amounts of sizing compositioncontained in the substrate of the present invention, combined with theabove-mentioned amounts of pigment, binder, nitrogen containingcompound, and inorganic salt; the amounts of each of the pigment,binder, nitrogen containing compound, inorganic salt that are containedin the paper may be easily calculated. For example, if 50 wt % ofpigment is present in the sizing solution based upon the total weight ofsolids in the composition, and the paper substrate contains 150 lbs ofthe sizing composition/ton, then the paper substrate contains 50%×150lbs/ton of paper=75 lbs pigment/ton of paper, which is 75 lbs/2000lbs×100=3.75 wt % pigment based upon the total weight of the papersubstrate.

The paper substrate contains any amount of at least one pigment. Thepaper substrate may contain from 0.5 wt % to 10 wt %, preferably from 1to 8 wt %, more preferably from 1.5 to 6 wt %, most preferably from 2 to5 wt % of pigment based upon the total weight of the substrate. Thisrange includes 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7,7.5, 8, 8.5, 9, 9.5 and 10 wt % of pigment based upon the total weightof the substrate, including any and all ranges and subranges therein.

The paper substrate contains any amount of at least one binder. Thepaper substrate may contain from 0.1 wt % to 7 wt %, preferably from 0.2to 5 wt %, more preferably from 0.3 to 3 wt %, most preferably from 1 to3 wt % of binder based upon the total weight of the substrate. Thisrange includes 0.1, 0.2, 0.3, 0.4, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5,5, 5.5, 6, 6.5, 7, and 7.5 wt % of binder based upon the total weight ofthe substrate, including any and all ranges and subranges therein.

The paper substrate contains any amount of at least one nitrogencontaining compound. The paper substrate may contain from 0.01 wt % to 5wt %, preferably from 0.05 to 2 wt %, more preferably from 0.1 to 1.5 wt%, most preferably from 0.25 to 1 wt % of nitrogen containing compoundbased upon the total weight of the substrate. This range includes 0.01,0.02, 0.03, 0.05, 0.07, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1,1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, and 3 wt % of nitrogencontaining compound based upon the total weight of the substrate,including any and all ranges and subranges therein.

The paper substrate contains any amount of at least inorganic salt. Thepaper substrate may contain from 0.001 wt % to 3 wt %, preferably from0.01 to 2.5 wt %, more preferably from 0.02 to 1 wt %, most preferablyfrom 0.05 to 0.5 wt % of inorganic salt based upon the total weight ofthe substrate. This range includes 0.001, 0.002, 0.005, 0.007, 0.01,0.02, 0.03, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6,0.7, 0.8, 0.9, 1, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, and 3 wt% of inorganic salt based upon the total weight of the substrate,including any and all ranges and subranges therein.

The paper substrate may contain any amount of OBA. The OBA may becationic and/or anionic. The OBA may be supplied by the sizingcomposition as mentioned above and/or within the substrate itself. Forexample, the OBA may be premixed with the fibers at the wet end of thepapermaking and even before the headbox. Preferred examples of usingOBA:fiber mixes is found in United States patent applications havingApplication No. 60/654,712 filed Feb. 19, 2005; 11/358,543 filed Feb.21, 2006; 11/445,809 filed Jun. 2, 2006; and 11/446,421 filed Jun. 2,2006, which are hereby incorporated, in their entirety, herein byreference.

In one embodiment of the present invention, the paper substrate containsinternal OBA and externally applied OBA. The internal OBA may becationic or anionic, but is preferably anionic. The externally appliedOBA may be cationic or anionic, but is preferably cationic. Theexternally applied OBA is preferably applied as a member of the sizingcomposition at the size press as mentioned above in the above preferredamounts of OBA. However, external OBA may also be applied at the coatingsection.

The paper substrate of the present invention may have any amount of OBA.In one embodiment, the OBA is present in as sufficient amount so thatthe paper has at least 80% GE brightness. The GE brightness ispreferably at least 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, and100%, including any and all ranges and subranges contained therein.

Further, the paper may have a suitable amount of OBA and other additives(such as dyes) so that the paper preferably has a CIE whiteness of atleast 130. The CIE whiteness may be at least 130, 135, 140, 145, 150,155, 160, 65, 170, 175, 180, 185, 190, 195, and 200 CIE whitenesspoints, including any and all ranges and subranges therein.

In one embodiment, the substrate contains an effective amount of OBA. Aneffective amount of OBA is such that the GE brightness is at least 90,preferably at least 92, more preferably at least 94 and most preferablyat least 95% brightness. The OBA may be a mixture of the above-mentionedinternal and externally applied OBA, whether cationic and/or anionic solong as it is an effective amount.

The density, basis weight and caliper of the web of this invention mayvary widely and conventional basis weights, densities and calipers maybe employed depending on the paper-based product formed from the web.Paper or paperboard of invention preferably have a final caliper, aftercalendering of the paper, and any nipping or pressing such as may beassociated with subsequent coating of from about 1 mils to about 35 milsalthough the caliper can be outside of this range if desired. Morepreferably the caliper is from about 4 mils to about 20 mils, and mostpreferably from about 7 mils to about 17 mils. The caliper of the papersubstrate with or without any coating may be 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 17, 20, 22, 25, 27, 30, 32, and 35, includingany and all ranges and subranges therein.

Paper substrates of the invention preferably exhibit basis weights offrom about 10 lb/3000 ft² to about 500 lb/3000 ft², although web basisweight can be outside of this range if desired. More preferably thebasis weight is from about 30 lb/3000 ft² to about 200 lb/3000 ft², andmost preferably from about 35 lb/3000 ft² to about 150 lb/3000 ft². Thebasis weight may be 10, 12, 15, 17, 20, 22, 25, 30, 32, 35, 37, 40, 45,50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150,160, 170, 180, 190, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425,450, 500 lb/3000 ft², including any and all ranges and subrangestherein.

The final density of the papers may be calculated by any of theabove-mentioned basis weights divided by any of the above-mentionedcalipers, including any and all ranges and subranges therein.Preferably, the final density of the papers, that is, the basis weightdivided by the caliper, is preferably from about 6 lb/3000 ft²/mil toabout 14 lb/3000 ft²/mil although web densities can be outside of thisrange if desired. More preferably the web density is from about 7lb/3000 ft²/mil to about 13 lb/3000 ft²/mil and most preferably fromabout 9 lb/3000 ft²/mil to about 12 lb/3000 ft²/mil.

The web may also include other conventional additives such as, forexample, starch, expandable microspheres, mineral fillers, bulkingagents, sizing agents, retention aids, and strengthening polymers. Amongthe fillers that may be used are organic and inorganic pigments such as,by way of example, polymeric particles such as polystyrene latexes andpolymethylmethacrylate, and minerals such as calcium carbonate, kaolin,and talc. Other conventional additives include, but are not restrictedto, wet strength resins, internal sizes, dry strength resins, alum,fillers, pigments and dyes. Internal sizing helps prevent the surfacesize from soaking into the sheet, thus allowing it to remain on thesurface where it has maximum effectiveness. The internal sizing agentsencompass any of those commonly used at the wet end of a paper machine.These include rosin sizes, ketene dimers and multimers, andalkenylsuccinic anhydrides. The internal sizes are generally used atlevels of from about 0.00 wt. % to about 0.25 wt. % based on the weightof the dry paper sheet. Methods and materials utilized for internalsizing with rosin are discussed by E. Strazdins in The Sizing of Paper,Second Edition, edited by W. F. Reynolds, Tappi Press, 1989, pages 1-33.Suitable ketene dimers for internal sizing are disclosed in U.S. Pat.No. 4,279,794, which is incorporated by reference in its entirety, andin United Kingdom Patent Nos. 786,543; 903,416; 1,373,788 and 1,533,434, and in European Patent Application Publication No. 0666368 A3.Ketene dimers are commercially available, as Aquapel® and Precis® sizingagents from Hercules Incorporated, Wilmington, Del. Ketene multimers foruse in internal sizes are described in: European Patent ApplicationPublication No. 0629741A1, corresponding to U.S. patent application Ser.No. 08/254,813, filed Jun. 6, 1994; European Patent ApplicationPublication No. 0666368A3, corresponding to U.S. patent application Ser.No. 08/192,570, filed Feb. 7, 1994; and U.S. patent application Ser. No.08/601,113, filed Feb. 16, 1996. Alkenylsuccinic anhydrides for internalsizing are disclosed in U.S. Pat. No. 4,040,900, which in incorporatedherein by reference in its entirety, and by C. E. Farley and R. B.Wasser in The Sizing of Paper, Second Edition, edited by W. F. Reynolds,Tappi Press, 1989, pages 51-62. A variety of alkenylsuccinic anhydridesare commercially available from Albemarle Corporation, Baton Rouge, La.

The paper substrate may be made by contacting further optionalsubstances with the cellulose fibers as well. The contacting of theoptional substances and the cellulose fibers may occur anytime in thepapermaking process including, but not limited to the thick stock, thinstock, head box, size press, water box, and coater. Further additionpoints include machine chest, stuff box, and suction of the fan pump.The cellulose fibers, components of the sizing composition, and/oroptional components may be contacted serially, consecutively, and/orsimultaneously in any combination with each other. The cellulose fiberscomponents of the sizing composition may be pre-mixed in any combinationbefore addition to or during the paper-making process.

The paper substrate may be pressed in a press section containing one ormore nips. However, any pressing means commonly known in the art ofpapermaking may be utilized. The nips may be, but is not limited to,single felted, double felted, roll, and extended nip in the presses.However, any nip commonly known in the art of papermaking may beutilized.

The paper substrate may be dried in a drying section. Any drying meanscommonly known in the art of papermaking may be utilized. The dryingsection may include and contain a drying can, cylinder drying, Condebeltdrying, IR, or other drying means and mechanisms known in the art. Thepaper substrate may be dried so as to contain any selected amount ofwater. Preferably, the substrate is dried to contain less than or equalto 10% water.

The paper substrate may be passed through a size press, where any sizingmeans commonly known in the art of papermaking is acceptable. The sizepress, for example, may be a puddle mode size press (e.g. inclined,vertical, horizontal) or metered size press (e.g. blade metered, rodmetered). At the size press, sizing agents such as binders may becontacted with the substrate. Optionally these same sizing agents may beadded at the wet end of the papermaking process as needed. After sizing,the paper substrate may or may not be dried again according to theabove-mentioned exemplified means and other commonly known drying meansin the art of papermaking. The paper substrate may be dried so as tocontain any selected amount of water. Preferably, the substrate is driedto contain less than or equal to 10% water. Preferably, the sizingapparatus is a puddle size press.

The paper substrate may be calendered by any commonly known calendaringmeans in the art of papermaking. More specifically, one could utilize,for example, wet stack calendering, dry stack calendering, steel nipcalendaring, hot soft calendaring or extended nip calendering, etc.While not wishing to be bound by theory, it is thought that the presenceof the expandable microspheres and/or composition and/or particle of thepresent invention may reduce and alleviate requirements for harshcalendaring means and environments for certain paper substrates,dependent on the intended use thereof.

The paper substrate may be microfinished according to any microfinishingmeans commonly known in the art of papermaking. Microfinishing is ameans involving frictional processes to finish surfaces of the papersubstrate. The paper substrate may be microfinished with or without acalendering means applied thereto consecutively and/or simultaneously.Examples of microfinishing means can be found in United States PublishedPatent Application 20040123966 and references cited therein, as well asU.S. Ser. No. 60/810,181 filed on Jun. 2, 2006, which are all hereby, intheir entirety, herein incorporated by reference.

The Hercules Sizing Test Value (“HST”) of the substrate is selected toprovide the desired waterfastness characteristics. The HST is measuredusing the procedure of TAPPI 530 pm-89. The paper substrate of thepresent invention may have any HST. In some embodiments, the HST may beas much as 400, 300, 200, and 100 seconds. Further, the HST may be is aslow as 0.1, 1, 5 and 10 seconds. However, in a preferred embodiment ofthis invention, the HST is less than 10 seconds, preferably, less than 5seconds, more preferably less than 3 seconds HST, most preferably lessthan about 1 second. The HST may be 0.001, 0.01, 0.05, 0.1, 0.5, 1, 1.5,2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 and 10seconds, including any and all ranges and subranges therein. As it iswell known to those of ordinary skill in the art, the HST will varydirectly with the basic weight of the substrate and other factors knownto those of ordinary skill in the art. Based upon the foregoinginformation, one of ordinary skill in the art can use conventionaltechniques and procedures to calculate, determine and/or estimate aparticular HST for the substrate used to provide the desired imagewaterfastness characteristics.

The paper substrate of the present invention may have any black opticaldensity as measured by TAPPI METHOD T 1213 sp-03. The black opticaldensity may be from 0.5 to 2.0, more preferably from 1.0 to 1.5. Theblack optical density may be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.05, 1.06,1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18,1.19, 1.2, 1.3, 1.4, and 1.5, including any and all ranges and subrangestherein.

From density, one can naturally calculate waterfastness using thefollowing equation:

(OD of soaked ink area/OD of unsoaked ink area)*100=%Waterfastness.

The paper substrate of the present invention may have any waterfastness.The paper substrate may have a waterfastness of at least 90%, preferablyat least 95%, more preferably greater than 98%, most preferably greaterthan 100%, including any and all ranges and subranges therein.

In one embodiment of the present invention, the paper substrate maycontain an effective amount of pigment and binder. An effective amountof pigment and binder is that which bestows on the paper a black opticaldensity that is at least 1.0, preferably from 1 to 2, more preferablyfrom 1 to 1.5 and most preferably from 1.1 to 1.3, including any and allranges and subranges therein.

The present invention relates to a method of decreasing the HST of apaper substrate. Preferably, the above-mentioned sizing composition iscontacted with a substrate having a first HST and containing a web ofcellulose fibers and optional substances mentioned above at a size pressor coating section so as to prepare a paper substrate having a secondHST that is less than the first HST and containing the sizingcomposition, the web of cellulose fibers, and optional substance. Whilethe second HST is less than the first HST, the present inventionpreferably reduces the first HST by at least 10%, more preferably by atleast 25%, most preferably by at least 50%. This reduction range may beat least 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 75, 80, 95 and 99% ofthe first HST, including any and all ranges and subranges therein.

The present invention is explained in more detail with the aid of thefollowing embodiment example which is not intended to limit the scope ofthe present invention in any manner.

EXAMPLES Example 1

The following size press formulations were prepared for treating theun-surface sized base paper.

TABLE 1 CHEMICALS 1 2 3 4 5 6 7 Jetcoat MD 1093 100 100 100 Precipitatedcalcium carbonate XC3310-1, ground calcium 100 100 carbonate TX-75NX,silica treated 100 calcium carbonate TX-75ZS, silica treated 100 calciumcarbonate Polyvinyl alcohol 20 10 10 10 10 Oxidized starch 30 60 60 100Cationic starch 100 60 Polydadmac 10 10 10 10 10 Calcium chloride 5 5 55 5 % solids 13 13 13 13 13 13 13 PH 6.7 7.0 7.3 7 6.9 6.8 69 Brookfiled27 46 80 55 118 38 27 viscosity Temperature, F. 117 120 117 130 130 130130

The pigmented size press formulations were applied to an unsurface sized90 gsm base paper using a rod metering size press. The target coatweight or pick up is 6 gsm. Calendaring was done on a steel-to-steel labcalendar at room temperature with a nip pressure of 90 psi. Thesmoothness target is 125 Sheffield smoothness.

TABLE 2 The paper samples from example 1 were evaluated for printperformance on an Kodak Versamark 5000 digital press. Excellent printquality were obtained. The print density test results on the trialsample provided in example 1 are list in the following table. Printdensity on Kodak Condition Versamark 5000 1 1.15 2 1.12 3 1.13 4 1.09 51.11 6 1.18 7 1.14

Example 2

Paper substrates having a basis weight of 24 lb/1300 square feet weremade and a sizing composition was applied thereto both surfaces of thepaper substrate at size press. The sizing compositions applied to thepaper substrate are those according to the following Table 2.

TABLE 2 Chem\Prop'ties\ functionality Cond'ns 1 2 3 4 5 SP puddle puddlePuddle puddle puddle configuration pigment (2) SMI JetCoat ® 100 30 SMIMD 1093 100 100 100 100 Binder (2) Clinton 442 60 60 60 60 60 starchMowiol 28-99 10 10 10 10 10 fixative (2) Gen Floc F71100 10 Cartafix VXZ10 10 15 15 salt (2) NaCl 8 8 8 8 8 CaCl2 5 brightener Leucophore 100(2) BCW (wet pts) Leucophore FTS 20 20 20 20 (wet pts) Wet-xer (1) Amres24 HP 5 5 properties target % solids 15 15 15 15 15 actual % solids 15.215.1 15.1 15.1 15.3 Brookfield #2 122 160 89 76 61 @ 50 rpm Brookfield#2 100 125 84 70 69 @ 100 rpm pH 8.0 7.3 7.8 7.8 7.0 Temperature 109 112147 140 143 Pickup 4.8 4.6 4.6 5.0 4.9 (lbs/3,300 ft2) pickup (gsm) 7.16.8 6.8 7.4 7.25 pickup (lbs/ton 157 151 151 164 161 of paper)OD_(ori[a]) 1.15/1.14 1.13/1.14 1.23/1.19 1.22/1.17 1.20/1.17OD_(soak&dry[a]) 1.13/1.19 1.14/1.19 1.22/1.19 1.22/1.17 1.19/1.17OD_(bleed[a]) 0.26/0.33 0.44/0.48 0.13/0.11 0.04/0.12 0.08/0.18 %Bleed_([a]) 22.83/29.13 39.26/42.00 10.35/8.85   2.76/10.41  6.42/15.47% H₂O fastness_([a])  97.78/104.08 100.98/105.05  99.60/100.42100.14/100.15  99.31/100.15

Gen Floc F71100 (General Chemicals) and Cartafix VXZ (Clariant) are bothof the chemical nature of poly(dadmac) and are nitrogen-containingspecies.

Amres, a kymene wet-strength resin from Kamira is alsonitrogen-containing species.

Mowiol 28-99 (Clariant) is a version of PVOH, which is 99% hydrolyzedand is of high molecular weight.

Starch and PVOH were cooked separately and diluted to a solids level ofabout 15%. Each of the formulation was prepared in accordance with therecipe as tabulated above and was thoroughly mixed together.

An overall % solids was first arrived at greater than the targeted 15%,because the rest of the ingredients all have a solids level above 15%.

For each of the formulations, the actual initial % solids was measuredand then diluted, as close as possible, to 15%. Each of the formulationswas sent to the 14″ pilot size press, which was pre-configured to C2Spuddle operation.

The paper after size press was dried to 4.2 to 5.0% moisture.

The subscript [a] denotes average, which means each of the numbers wasaveraged from 4 or even more readings.

The two numbers before and after the slash sign represent readings fromthe two sides of the paper, respectively.

Ink jet print densities are measured by means of optical densities withan X-rite densitometer. The density according to TAPPI METHOD T 1213sp-03 is the optical-negative logarithm to base 10 of transmittance fortransparent material or the reflectance for an opaque material and hasthe equation Optical Density=log 10 1/R, where R=Reflectance. Thefollowing densitometer was used: X-Rite Densitometer, manufactured byX-Rite Inc. Density is a function of the percentage of light reflected.From this density procedure, one can easily measure Waterfastness and %bleed as well using the following equations:

(OD of soaked ink area/OD of unsoaked ink area)*100=%Waterfastness  Calculation for % Waterfastness:

[(OD near soaked ink area−OD of paper)/OD unsoaked inkarea]*100=%Bleed.  Calculation for % Bleed:

Numerous modifications and variations on the present invention arepossible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the accompanying claims, theinvention may be practiced otherwise than as specifically describedherein.

As used throughout, ranges are used as a short hand for describing eachand every value that is within the range, including all subrangestherein.

All of the references, as well as their cited references, cited hereinare hereby incorporated by reference with respect to relative portionsrelated to the subject matter of the present invention and all of itsembodiments

1) A sizing composition, comprising at least one pigment at least onebinder; at least one nitrogen containing organic species; and at leastone inorganic salt. 2) The sizing composition according to claim 1,comprising at least one pigment at least two binders; at least onenitrogen containing organic species; and at least one inorganic salt.3.) The sizing composition according to claim 2, wherein the at leasttwo binders are polyvinyl alcohol and starch. 4.) The sizing compositionaccording to claim 3, wherein the polyvinyl alcohol and starch arepresent at a starch/polyvinyl alcohol weight ratio of from 8/1 to 1/1.5.) The sizing composition according to claim 4, wherein the totalbinder is present at an amount ranging at least 20 wt %, based upon thetotal weight of the solids in of the composition. 6.) The sizingcomposition according to claim 4, further comprising from 20 to 40 wt %based on the total weight of the solids in the composition of an opticalbrightening agent. 7.) The sizing composition according to claim 4,further comprising an optical brightening agent. 8.) The sizingcomposition according to claim 8, wherein the optical brightening agentis cationic. 9.) The sizing composition according to claim 1, comprisingat least one pigment at an amount of at least 30 wt % based upon thetotal weight of the solids in of the composition at least one binder atan amount of at least 20 wt % based upon the total weight of the solidsin of the composition; at least one nitrogen containing organic speciesat an amount ranging from 1 to 20 wt % based upon the total weight ofthe solids in of the composition; and at least one inorganic salt at anamount ranging from 0.5 to 5 wt % based upon the total weight of thesolids in of the composition. 10.) The sizing composition according toclaim 9, comprising at least two binders wherein the at least twobinders are starch and polyvinyl alcohol at a weight ratio of from 8/1to 1/1 starch/polyvinyl alcohol; and an optical brightener. 11.) A papersubstrate, comprising the sizing composition according to claim
 1. 12.)The paper substrate according to claim 11, wherein the substrate has aprint density of at least 1.0 and an HST of not more than 10 seconds.13.) The paper substrate according to claim 12, wherein the substratehas a waterfastness of at least 95%. 14.) A paper substrate comprisingthe sizing composition according to claim
 4. 15.) The paper substrateaccording to claim 14, wherein the substrate has a print density of atleast 1.0 and an HST of not more than 10 seconds. 16.) The papersubstrate according to claim 15, wherein the substrate has awaterfastness of at least 95%. 17.) A paper substrate comprising thesizing composition according to claim
 9. 18.) The paper substrateaccording to claim 17, wherein the substrate has a print density of atleast 1.0 and an HST of not more than 10 seconds. 19.) The papersubstrate according to claim 18, wherein the substrate has awaterfastness of at least 95%. 20.) A paper substrate, comprising thesizing composition according to claim 10 and having a print density ofat least 1.0; an HST of not more than 10 seconds; and a waterfastness ofat least 95%.